The ability of cancer cells to detoxify various chemotherapy and radiosensitizing agents has important clinical implications in cancer treatment. One pathway in particular utilizes the important redox molecule, glutathione (GSH), to chemically conjugate alkylating agents and thus limit their effectiveness as cytotoxic agents. We have maintained a steady interest in the role that GSH may play in vivo in the development of resistance to these class of cancer drugs. One aspect which we began last year was to determine how various GSH depleting or modifying agents would effect the various subpopulations which make up the local tumor environment. To this end we are utilizing magnetic beads, conjugated with anti-CD45 antibodies, to remove from rodent tumor cell preparations leukocytes, which often comprise about 45-60% of a tumor preparation. Our purpose is to examine how these two different cell populations respond to various GSH modifying agents. We have perfected this technique and now are in the process of using it to separate and measure GSH, GSSG, and other redox molecules in both purified leukocyte and tumor populations. In addition, with our HPLC technique we can also quantify GSNO which is also thought to have important regulatory properties. We are also interested in quantitating the extent of apopotosis after various treatments (either with drugs or radiation) in both the tumor and leukocyte populations using Apo-tag kits which end label damaged DNA with a fluorescent agent. These observations may have important clinical implications with regards to how each subpopulation in a tumor mass responds to treatment and how this translates into a 'tumor response'.